As people pay attention to their health, more and more people would like to daily take some vitamins and healthy dietary components to keep their health. These vitamins and healthy dietary components include fat-soluble nutrients such as VA, VE, and VD3; polyunsaturated fatty acids such as ω-3, ω-6, and ω-9; carotenoids such as beta-carotene, lutein, zeaxanthin, astaxanthin, ycopene, and curcumin; as well as retinoids such as coenzymes Q10.
Because of multiple double bonds in the molecular structures of these nutrients, these nutrients have health functions. These double bonds can highly eliminate free radicals in the human body and have antioxidant ability. Free radicals are one of the most important reasons of producing aging and other diseases. It has been estimated that 80%-90% of aging and degenerative diseases are associated with free radicals, wherein these diseases include cancer, Alzheimer's disease, Parkinson's disease, skin spots deposition, cataract, heart disease and so on. So it is of great importance for keeping one's body healthy and young to eliminate harmful free radicals.
These nutrients have the following structure and efficacy:
Vitamin A
Vitamin A is a very important member in the fat-soluble nutrients family and has a very important function on visual health, bone health, reproduction and cell division and reproduction. It would be inconceivable for the lack of vitamin A in the human body. Vitamin A mainly exists in the form of vitamin A alcohol (structure provided below), vitamin A acetate and vitamin A palmitate.
Vitamin E
Vitamin E is an important anti-oxidation agent derived from nature and synthesis. Vitamin E exists in eight forms of monomers such as alpha-vitamin E, beta-vitamin E, gamma-vitamin E, and delta-vitamin E, each of the monomers has two different optical isomers. Alpha-Vitamins E including such as free type tocopherol, tocopherol acetate, tocopherol succinate and tocopheryl nicotinate are widely used in the market.
Polyunsaturated Fatty Acids (PUFA)
Polyunsaturated fatty acids are essential for the human body and mainly play a role on physiological functions such as maintaining cell membrane fluidity to assure normal physiological function of cells, promoting cholesterol esterfication, reducing cholesterol and triglycerides levels of blood, decreasing blood viscosity, and improving blood circulation, increasing activity of brain cells and enhancing memory and improving human thinking.
Polyunsaturated fatty acids mainly comprises ω-3 PUFA such as α-linolenic acid, Eicosapentaenoic acid, Docosahexaenoic acid and docosapentaenoic acid and ω-6 PUFA such as Linoleic acid, Conjugated Linoleic acid, γ-Linolenic, Arachidonic Acid. The molecular structures of these polyunsaturated fatty acids are as follows:

The fish oils derived from abyssopelagic fishes such as anchovy, tuna and squid mainly comprise polyunsaturated fatty acids EPA and DHA. DHA and EPA are also derived from cultured algae.
Carotenoids
Carotenoids are synthesised by plants and exist in nature in the form of pigments. There are more than 600 kinds of known carotenoids, wherein beta-carotenoids, lycopene, astaxanthin, lutein and cryptoxanthin are more important carotenoids. Some carotenoids can be converted to Vitamin A having physiological effects on the human body and the animal body and thus are known as “provitamin A”.
Carotenoids have main functions as follows: the most effective antioxidants against free radicals; enhancing immune system, increasing resistibility; preventing or fighting against cancer; decreasing risks of oral cancer, breast cancer, cervical cancer, lung cancer, trachea cancer, esophagus cancer, stomach cancer, bladder cancer; preventing heart and vascular diseases; preventing cataract, protecting fiber parts of eyes crystal; improving urinary system, preventing prostate problem; improving tendonitis and adhesive capsulitis caused by rheumatic arthritis tendinitis, being natural eye drops, maintaining lubrication and transparency of cornea and promoting health of eyes; being the precursor of VA, keeping healthy of skin and organ cavity mucosa.
Curcumin
Curcumin is a very prospective nutrient and has functions such as resisting oxidation, scavenging free radicals, anti-inflammatory, anti-freezing, regulating blood lipid, anti-lipid peroxidation, inhibiting formation of plaque, inhibiting proliferation of vascular smooth muscle cells. Its molecular structures is as follows:
Coenzymes Q10
Coenzyme Q10 is a fat-soluble compound widely existing in organisms and widely distributed in nature, mainly in yeast, plant leaves, seeds and cells of heart, liver and kidney of animals. Coenzyme Q10 is one of the most important coenzymes in the human body. The main function of coenzyme Q10 is to scavenge free radicals, anti-tumor activity, enhance immunity, promote metabolism and improve hypoxia tolerance of the heart, etc.

It may be seen that the above nutrients have at least two common features: 1) having fat-soluble characteristics, and 2) having multiple double bonds in the molecular structure.
It would highly limit their application scopes and application modes due to fat-soluble characteristics. So their nutrients are used in the oil-based food or administered in the form of soft capsules or modified to become water soluble and thus used in the water-based foods. An important method of changing its solubility is to change fat-soluble nutrients into water soluble nutrients by microcapsules.
On the one hand, multiple double bonds provide the nutrients for antioxygenic property and scavenging free radicals and reflecting its physiological function. On the other hand, multiple double bonds make the nutrients very unstable in the storage process or in the process of microcapsule processing because of heat and light and consequently cause the nutrients to have reduced biological activity, especially it makes a degradation process more obvious in higher pressure and heating.
Many methods for preparing fat soluble nutrient microcapsules have been reported in the prior art.
US Patent No. 2007/0128341 discloses a method of preparing polyunsaturated fatty acids by lactoprotein, in particular a method of preparing a polyunsaturated fatty acid microcapsule emulsion or powders from fish oils by using lactoprotein and polyunsaturated fatty acids, to obtain a microcapsule.
US Patent No. 2008/0254184 describes a formulation and method of preparing polyunsaturated fatty acids microcapsule using Arabic gum. But the method only uses Arabic gum in the capsule shell materials. It certainly limits its application.
Chinese Patent No. 101177540B discloses a method of preparing water-soluble carotenoids microcapsule powder. In particular, carotenoids dissolved in organic solvents are mixed with water and homogenized under high pressure, high temperature and high viscosity to obtain an emulsion. A great amount of water is added for reducing the viscosity of the emulsion due to high pressure in the process. It certainly produces waste of energy and operation because of removing the water before spraying and prilling.
Chinese Patent No. 1022278257A relates to a method of preparing an algal oil DHA (Docosahexaenoic Acid) microcapsule. In particular, modified starch and Arabic gum as capsule shell materials are added in separate steps, and then an emulsifier, an aqueous phase, an emulsion phase and a combined phase, emulsion are respectively prepared. The process goes through several mixing, shearing, and homogenization. And a greater amount of water is added to achieve homogenization effects. Especially the requires removing water before spraying and drying. So the process is long and complex, with a low degree of efficiency.
In general, some products made by the methods of preparing fat-soluble nutrients microcapsule containing multiple double bonds in the art have poor stability, fall short of expectation, complex process, lower efficiency; and severe conditions. It would be very difficult to achieve in the industry. So it is necessary to find a simple method for preparing a highly stable, water soluble microcapsule.
The inventors of the present invention found that the stability of fat-soluble nutrients microcapsule containing multiple double bonds has something to do with not only the formulation but also the processing technology of the process. For example, the stability of the final microcapsule product is closely related to emulsion degrees of aqueous phase and oil phase, and sizes of oil-in-water emulsion. The more uniform a mixture of oil phase and aqueous phase is, the smaller particle diameter of oil droplet oil in water emulsion droplet is, the more stable is the final microcapsule product. That is why the oil phase and the aqueous phase are completely mixed during the preparation process of microcapsule and the obtained emulsion needs conducting high pressure homogenization.
After shearing and emulsifying, the particle diameter of the emulsion droplet is micron-sized. the emulsion containing bigger particle diameter droplet is homogenized under a high pressure (generally more than 10 Mpa) to improve the stability of final product. After homogenization, the micron-sized droplets are smashed smaller up to nanoscale droplets. These nanoscale droplets are to the benefit of not only increasing the bioavailability of final product, but also being completely embedded, in order to prevent from aggregation of larger-sized particles and improve the stability of final product.
During the process of homogenizing micron-sized droplets emulsion under high pressures, the homogenization effect of the emulsion is closely related to the viscosity of the emulsion. The smaller the viscosity is, the lower the homogenization pressure is, the better the homogenization effect is. It means that the smaller the particle diameter of oil in water emulsion droplet is, the more stability the final microcapsule product has. Besides, the emulsion can obtain more energy in high pressures of homogenization due to high pressure functions, so as to make emulsion temperature increased more easily, even up to more than 20° C. The higher the pressure is, the more the emulsion temperature rises. But increasing the emulsion temperature is very unfavorable for the stability of nutrients containing multiple double bonds. On the one hand, increasing temperature may easily degrade these unstable nutrients, and even may produce some new unexpected degradation products. On the other hand, existing in a high temperature for a long time will make the microcapsule product unstable. It means that the stability of lots of fat-soluble nutrients microcapsule products containing multiple double bonds, especially polyunsaturated fatty acid microcapsule powders from fish oils, is not good. The content of effective components will decrease over time. This is why the product produces an obvious fishy odor after storage for quite a while. These problems cannot be effectively solved, even though taking various measures such as adding numbers of antioxidants, double encapsulating, and increasing proportion of capsule shell materials.